Filtering systems for separating solids from a liquid in a suspension become clogged by the solids of the suspension deposited on the outside surface of its screen over a period of time. The screen must be periodicly cleaned to remove the solids deposited on the screen. Usually, the screen or the entire filter must be taken out of the suspension to be cleaned, disrupting the liquid flow through the filter for a significant time period.
Filtering systems in large power plants, such as for steam turbine generators, supply water as coolant for their operation. In a steam turbine generator a large quantity of cooling water is needed for the condenser. Accordingly, the plants are situated adjacent large bodies of water so that cooling water can be easily obtained as needed. However, before such water can be used as a cooling agent, it must first pass through a filter to prevent any solid particles contained in the water from entering the condensor.
After a short period of time these filters tend to collect solid materials, such as wood chips, leaves, grass, fish and other debris on their outer exposed surfaces. This large amount of debris rapidly covers the screen, greatly reducing and even stopping the flow of water through the screen and into the intake for the condenser.
Conventional devices for cleaning the filter screens are disclosed in U.S. Pat. Nos. 4,169,792 to Dovel; 4,518,494 to Jackson; and 4,565,631 to Bitzer et al. However, these conventional cleaning devices suffer from many disadvantages. The devices requiring moving screens or mechanisms are costly to manufacture and to maintain. Some include special movable dividers for causing a backflow or require a reciprocating rake mechanism to clean the filter screen. It is also known to use an air backwash system which releases compressed air within the filter for causing a backwash through the filter screen removing solids deposited thereon.